Solar thermoelectric generator

Patent metadata

Field	Value
Publication number	US-9331258-B2
Application number	US-201414190064-A
Country	US
Kind code	B2
Filing date	Feb 25, 2014
Priority date	Feb 25, 2013
Publication date	May 3, 2016
Grant date	May 3, 2016

Abstract

Solar thermoelectric generators (STEGs) are solid state heat engines that generate electricity from concentrated sunlight. A novel detailed balance model for STEGs is provided and applied to both state-of-the-art and idealized materials. STEGs can produce electricity by using sunlight to heat one side of a thermoelectric generator. While concentrated sunlight can be used to achieve extremely high temperatures (and thus improved generator efficiency), the solar absorber also emits a significant amount of black body radiation. This emitted light is the dominant loss mechanism in these generators. In this invention, we propose a solution to this problem that eliminates virtually all of the emitted black body radiation. This enables solar thermoelectric generators to operate at higher efficiency and achieve said efficient with lower levels of optical concentration. The solution is suitable for both single and dual axis solar thermoelectric generators.

First claim

The invention claimed is:

1. A solar thermoelectric generator comprising:
an optical concentrator to concentrate solar flux at a focal point;
a non-uniform cavity comprising:
a first end positioned proximate to the focal point, the first end comprising an aperture at the focal point;
a closed end positioned opposite the first end, the closed end comprising an upwardly-oriented surface facing the aperture; and
one or more side walls extending upwardly from the upwardly-oriented surface of the closed end to the first end, the one or more side walls having an interior surface;

a thermal absorber interconnected to the closed end of the non-uniform cavity and positioned below the non-uniform cavity, the thermal absorber comprising:
an upper surface facing the aperture of the non-uniform cavity and which has energy-dependent absorbtivity and emissivity, wherein the upper surface of the thermal absorber is positioned at the closed end of the non-uniform cavity and forms a portion of the upwardly-oriented surface of the closed end of the non-uniform cavity, wherein the aperture of the non-uniform cavity comprises a surface area which is smaller than a surface area of the upper surface of the thermal absorber, and wherein the interior surface of the one or more side walls of the non-uniform cavity comprises a reflective material to reflect emitted radiation to the upper surface of the thermal absorber; and
a lower surface opposite the upper surface of the thermal absorber;

a thermoelectric module positioned below the thermal absorber and in direct contact with the lower surface of the thermal absorber, the thermoelectric module comprising:
a first thermoelectric leg comprising p-type material and having a hot end and a cold end, wherein the hot end is interconnected to the lower surface of the thermal absorber,
a second thermoelectric leg comprising n-type material and having a hot end and a cold end, wherein the hot end is interconnected to the lower surface of the thermal absorber; and
an electrical connector to electrically connect the cold end of the first thermoelectric leg to the cold end of the second thermoelectric leg; and

a cooling system positioned below and in direct contact with the cold end of the first thermoelectric leg and the cold end of the second thermoelectric leg.

2. The solar thermoelectric generator of claim 1 , wherein the aperture is at least one of a pin-hole and a slit.

3. The solar thermoelectric generator of claim 1 , wherein the upper surface of the thermal absorber comprises a first layer, a second layer, and a substrate.

4. The solar thermoelectric generator of claim 3 , wherein the first layer is a dielectric material and the second later is a metal material.

5. The solar thermoelectric generator of claim 1 , wherein the upper surface of the thermal absorber comprises two or more selective absorber films.

6. The solar thermoelectric generator of claim 1 , further comprising a vacuum enclosure positioned around the thermoelectric module, the thermal absorber, and at least a portion of the non-uniform cavity.

7. The solar thermoelectric generator of claim 1 , wherein the non-uniform cavity comprises at least one photonic surface on the interior surface of the one or more side walls which create angular-emission restrictions to decrease radiative losses.

8. The solar thermoelectric generator of claim 7 , wherein the one or more side walls have low thermal conductivity such that the one or more side walls are thermally insulating.

9. The solar thermoelectric generator of claim 1 , wherein the thermoelectric module further comprises insulation.

10. A solar thermoelectric generator comprising:
an optical concentrator adapted to receive and concentrate a solar flux at a focal point;
a thermal absorber positioned below the optical concentrator, the thermal absorber comprising a first surface which has energy-dependent absorbtivity and emissivity and a second surface opposite the first surface;
a thermoelectric module interconnected to the second surface of the thermal absorber and positioned below the second surface of the thermal absorber, the thermoelectric module comprising:
(i) a first thermoelectric leg comprising a first end and a second end, wherein the first end is provided in direct contact with the second surface of the thermal absorber; and
(ii) a second thermoelectric leg comprising a first end and a second end, wherein the first end is in direct contact with the second surface of the thermal absorber, and wherein the first thermoelectric leg is provided in electrical communication with the second thermoelectric leg; and

an enclosure extending upwardly from the first surface of the thermal absorber, for receiving and reflecting at least a portion of the solar flux from the optical concentrator, the enclosure comprising:
(i) an upper portion having an aperture positioned at the focal point of the solar flux;
(ii) a lower portion positioned below the upper portion and in direct contact with the thermal absorber, wherein the lower portion is a closed end;
(iii) a predetermined height between the upper portion and the lower portion;
(iv) one or more walls extending from the closed end to the aperture; and
(v) an internal non-uniform cavity;

wherein the aperture receives at least a portion of the solar flux from the optical concentrator and transmits the at least a portion of the solar flux to the internal non-uniform cavity,
wherein the first surface of the thermal absorber is oriented toward the aperture and the internal non-uniform cavity,
wherein an interior surface of the one or more walls reflect emitted radiation to the first surface of the thermal absorber, and
wherein the first surface of the thermal absorber absorbs at least a portion of the solar flux.

11. The solar thermoelectric generator of claim 10 , further comprising a vacuum enclosure positioned around the thermoelectric module, the thermal absorber, and at least a portion of the enclosure.

12. The solar thermoelectric generator of claim 10 , wherein the enclosure comprises a frustoconical member.

13. The solar thermoelectric generator of claim 10 , wherein the aperture comprises a surface area which is smaller than a surface area of the first surface of the thermal absorber.

14. The solar thermoelectric generator of claim 10 , further comprising a cooling system in thermally conductive communication with at least one of the first thermoelectric leg and the second thermoelectric leg.

15. A method of manufacturing a solar thermoelectric generator according to claim 10 comprising:
providing an optical concentrator adapted to concentrate a solar flux;
providing a thermal absorber comprising a first surface which has energy-dependent absorbtivity and emissivity, and a second surface opposite the first surface;
providing a thermoelectric module proximal to the thermal absorber,
providing an enclosure for receiving and reflecting at least a portion of the solar flux, the enclosure comprising:
(i) an upper portion;
(ii) a lower portion proximal to the thermal absorber; and
(iii) an internal cavity comprising a reflective material;

providing an aperture in the upper portion of the enclosure;
receiving at least a portion of the solar flux from the optical concentrator,
transmitting the at least a portion of the solar flux through the aperture to the thermal absorber;
reflecting solar flux emitted from the thermal absorber back to the thermal absorber, and
converting the solar flux into electricity.

16. The method of manufacturing a solar thermoelectric gene

Assignees

• Colorado School Of Mines

Inventors

• Toberer Eric S
• Baranowski Lauryn L
• Warren Emily L

Classifications

• F24S20/20

  Solar heat collectors for receiving concentrated solar energy, e.g. receivers for solar power plants · CPC title

• F24S10/45

  the enclosure being cylindrical · CPC title

• F24S80/54

  using evacuated elements · CPC title

• H01L35/34

  Electricity · mapped topic

• F24J2/055

  Mechanical Engineering · mapped topic